1. Field of the Invention
The present invention concerns a wide pleasure boat or cruise ship of the kind having an open or semi-open main public space bordered by longitudinal superstructures.
In the present description and in the claims:                the expression “main public space” designates a space of substantial size comprising one or more areas dedicated primarily to the use of passengers;        the expression “open main public space” designates a main public space which is open to the outside, primarily at the top;        the expression “semi-open main public space” designates an open main public space to which one or more fixed or mobile elements have been added, primarily at the top, whose function is to keep out sun, wind and inclement weather;        the expressions “length” and “width” respectively designate the dimension in the longitudinal direction of the ship (normal direction of forward movement) and the dimension in the transverse direction of the ship;        the expression “set of superstructures” designates the portion of the ship situated above the mean level of the compartmentalization deck, which deck covers the watertight compartmentalization bulkheads;        the expression “longitudinal superstructure” designates a substantial portion of the set of superstructures whose length is greater than the width; and        the expression “classically proportioned quickwork” designates quickwork for which the ratio of the length at the waterline to the width at the waterline is from 4 to 10, as in most present-day ferries and pleasure boats.        
2. Description of the Prior Art
Cruise ships and pleasure boats (large yachts) are usually single-hull vessels with decks whose width is identical or close to the width of the ship at the waterline. The open or semi-open public spaces are generally on the upper decks. To meet an ever increasing demand to increase the density of cabins and other areas giving onto the outside, some ship designs have a longitudinal main public space bordered by port and starboard vertical longitudinal superstructures primarily accommodating cabins with an outside view, either toward the sea if they are on the side away from the axis of the ship or toward the main public space in question if they are on the side near the axis of the ship. These ship designs have a total width equal to or close to their width at the waterline. If the ship is a single-hull vessel, its substantially U-shaped cross section cannot provide a volume of air above the main public space wide enough for the public space and the cabins and other areas giving onto it to be user-friendly, pleasant and sufficiently sunny. Widening the entire ship is not advantageous, in particular because of uncomfortable rolling (the natural period of rolling of the ship would become too short); this problem can be solved by producing a multiple-hull ship, which has other drawbacks such as the high cost of building the underwater portions.
The present invention aims to avoid the above problems by using a new design principle which provides many outdoor spaces or spaces giving onto the outdoors that are user-friendly and functional but satisfy comfort and safety requirements.